There are two predominant categories of locks: cylindrical locks and mortise locks. Mortise locks were the first type of locksets to be mass produced. A mortise lock comprises a lock box body full of cams and levers. It is expensive to produce. Furthermore, to install a mortise lock, a large amount of material must be cut out of the edge of the door to accept the lock body. This requires special tools and a high skill level.
Early in the twentieth century, Dexter Locks™ introduced a new type of lock that had less complex parts. To mill a door to accept the lock required only drilling a cylindrical hole through the face of the door and drilling another hole from the edge intersecting with the face hole. Since the required preps were cylindrical holes, these locks were called cylindrical locks. From the time of their introduction, the cylindrical lock rapidly grew in popularity. Because of the lower manufacturing cost and sales prices and ease of installation, they became the most popular lock type used. Currently 99 percent of the locks sold in the United States, both in the commercial and residential market, are cylindrical locks.
Deadbolt locks come in both mortise and cylindrical varieties, with the vast majority being cylindrical. There are two basic types of cylindrical deadbolt: the single cylinder deadbolt and the double cylinder deadbolt. The single cylinder deadbolt has a key on the outside and a thumb turn on the inside. A double cylinder deadbolt has a cylinder on both sides and requires a key to lock or unlock the deadbolt from either side of the door.
Contemporary building and fire codes do not allow cylinder deadbolts on doors in a path of egress (the path of exit) unless the locking device is readily distinguishable as locked and a readily visible, durable sign is posted on the egress side on or adjacent to the door stating: “THIS DOOR TO REMAIN UNLOCKED WHEN BUILDING IS OCCUPIED.”
The predominant indicator available in the market today is the Adams Rite™ indicator. However, it only works in conjunction with mortise locks. The use of the Adams Rite™ indicator requires special milling and mortising of a door that is not common in either the residential or the commercial door marketplace.
Applicant is unaware of any indicator deadbolt that fits the code requirements and fits the most common lock prep, the cylindrical lock. If a door has been machined for a cylindrical lock, then the Adams Rite™ lock cannot be installed without great expense or rework to the door. So, if a door has been machined for a cylindrical deadbolt and is in the path of egress, there are currently no locks or solutions that will allow the door owner to meet the egress codes without encountering great expense.
Contractors frequently fail their final fire inspection for having a deadbolt that does not meet the code requirements for lack of an indicator. They are faced with replacing the door or having it patched and remachined for the Adams Rite™ indicator or simply removing the deadbolt. In most cases the deadbolt was installed because the added security was needed. Removal opens up the end user to more liability and possible theft. The most common resolution to this dilemma is for the contractor to remove the deadbolt and put a filler plate into the hole left by the deadbolt. They pass their inspection and tell the owner they are not allowed to have a deadbolt on the door by code, but if they want it they can install it themselves when the contractor is done with the project. Frequently, the building owner will reinstall the deadbolt even though it is in violation of life safety codes and is unsafe.